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Endocrinology > Reproduction/ Sex steriod axis > Flashcards

Reproduction/ Sex steriod axis Flashcards

(53 cards)

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1
Q

what 2 gonadotrophic hormones are secreted by the pituitary gland

A

FSH and LH

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2
Q

what does FSH do in males

A

causes the testes to produce sperm

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3
Q

what does FSH do in females

A

causes the growth of ovarian follicles (oogenesis) and causes the ovary to secrete oestrogen

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4
Q

what does LH do in males

A

causes the testes to secrete testosterone

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5
Q

what does LH do in females

A

causes ovulation and progesterone production by the corpus luteum

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6
Q

how does testosterone affect levels of LH, FSH and GnRH

A

when high will reduce the levels of LH and FSH and GnRH by negative feedback HPG axis

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7
Q

what is the HPG axis

A

hypothalamus - anterior pituitary - LH and FSH - ovaries (oestrogen and progesterone) and testes (testosterone)

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8
Q

what hormone causes the release of FSH and LH from the anterior pituitary

A

gonadotrophin releasing hormone GnRH)

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9
Q

what type of hormone if GnRH and what makes and releases it

A

neuropeptide hormone

made and released by GnRH neurones within the hypothalamus

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10
Q

how is GnRH released in both males and females

A

in a pulsatile manner

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11
Q

what is the different between GnRH secretion in males and females

A

males- constant pulses

females- frequency of pulses varies depending on menstrual cycle (1-2 hours during early follicular phase, decreasing to 4 hours during luteal phase)

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12
Q

what do high frequency GnRH pulses stimulate

A

LH pulses

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13
Q

what do low frequency GnRH pulses allow

A

FSH release

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14
Q

how does oestrogen affect GnRH

A

high oestrogen (above 200) will increase GnRH pulsatility driving the release of LH

below 200 reduces frequency of GnRH pulses (FSH release)

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15
Q

why is modulation of LH pulse frequency needed

A

for pubertal maturation and reproductive function

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16
Q

what happens to GnRH in the onset of pubertal maturation

A

steady acceleration i GnRH pulsatility (peak at night- boys causes peak in testosterone in morning, erections)

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17
Q

what are the signs of delayed puberty

A

no period by age of 15

boys no sign of testicular development by age 14

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18
Q

how is GnRH pulsatility regulated

A

GnRH neurones activated by kisspeptin as dont have receptors for oestrogen and progesterone (the hormonal regulators)

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19
Q

what is the variable part of the menstrual cycle

A

follicular (proliferative phase) typically 14 days +/- 7 days

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20
Q

what is the follicular phase characterised by

A

follicular growth

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21
Q

what is the more constant phase of the menstrual cycle

A

luteal phase (secretory phase)

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22
Q

what causes the LH surge

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A

when high oestrogen causes positive feedback

23
Q

why does FSH cause an increase in oestrogen

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A

as follicles produce oestrogen

24
Q

what does LH surge causes

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A

ovulation, regulates the formation of the corpus luteum, progesterone production and secretion (from follicle)

25
how does increasing progesterone affect LH
decreases LH secretion by influencing GnRH pulsatility
26
what does increasing progesterone do to LH secretion
decreases it by influencing GnRH pulsatility
27
what hormone dominates the luteal phase
progesterone
28
what makes up a follicle
an oocyte surrounded by folicular cells (granulosa cells, theca cells)
29
happens happens to the follicle during its growth
increase in the number of follicular cells and accumulation of follicular fluid (increases in diameter and size)
30
what effect does oestrogen have on the endometrium
thickens
31
what effect does progesterone have on the endometrium
causes it to become a secretory tissue
32
what hormone stimulates follicular growth
FSH (granulosa cells) | LH (theca cells)
33
what happens in follicular growth if there is a lack of FSH
build up of androgens
34
how many follicles in each ovary
7 million 2 million at birth 0.5 million at puberty
35
how can FSH determine if a follicle is lost or not
when reaches certain size follicle becomes gonadotrophin dependent (2-5mm), if this doesnt coincide with rise in FSH during early follicular phase then follicle is lost
36
how many follicles are selected for ovulation
1 (5/6 grow during each menstruation)
37
what can predict the timing of ovulation
the LH surge (precedes ovulation by 34-36 hours)
38
what happens to progesterone in LH surge
increases- essential for ovulation as stimulates enzymes that break down follicular wall releasing enzymes
39
what hormone causes the formation of the corpus luteum
LH
40
how do cells form the corpus luteum
granulosa and theca cells transform into luteal cells
41
how does LH cause the formation of the luteal corpus
``` stimulates angiogenesis (ensures delivery of cholesterol which is the synthesis for progesterone synthesis) stimulates enzymes involved in conversion of cholesterol to progesterone ```
42
what are the functions of oestrogens
increases the thickness of the vaginal wall regulate the LH surge reduce vaginal pH though increase in lactic acid production decreased viscosity of cervical mucous to facilitate sperm penetration
43
what is the role of progesterone
``` maintains the thickness of the endometrium creates infertile thick mucous (prevents sperm and infection) relaxes myometrium (smooth muscle) important in maintaining pregnancy ```
44
what hormones control spermatogenesis
LH and FSH and testosterone
45
how long does spermatogenesis take
70 days
46
what makes up the testes
seminiferous tubules surrounded by interstitial tissue
47
what is in the intratubular compartment of the testes
sertoli and germ cells
48
where does spermatogenesis take place
in the seminiferous tubules in the testes
49
what is in the seminiferous tubules
sertoli cells and maturing germ cells surrounded by peritubular myoid cells
50
what cells are stimulated by FSH to start spermatogenesis
sertoli cells
51
what receptors do leyid cells (in testes) have
LH receptors- when bound secrete testosterone
52
what paracrine factors affect spermatogenesis
testosterone and inhibin
53
what is the role of testosterone in spermatogenesis
maintains the blood testes barrier | causes the release of mature spermatozoa from sertoli cells by influencing peritubular myoid cells

Endocrinology (46 decks)

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